It is known in the art to apply mixtures of organic materials containing metals such as chrominum, iron and cobalt to a heated glass surface in order to develop a coating on that surface consisting of the oxides of the three mentioned metals. When the organic based material is applied to a heated glass sheet, the organic portion of the spray volatilizes leaving the oxide form of the metal therebehind.
I have discovered that if the composition of the coating on the glass surface falls within a certain range with respect to the chromium, iron and cobalt oxide content thereof, the coating is more durable than coatings having compositions falling outside of the particular area I have discovered. I have also tested compositions available on the commerical market. These compositions are glasses having a coating thereon consisting of the oxides of chromium, iron and cobalt. In each case, I have found that the commerically available coated glass substrates have oxide compositions falling outside of the range I now find to be the range of the most durable films. In each case, the coated glass product avialable to the commercial market did not have the superior surface coating qualities that I have found if the oxide composition on the glass surface falls within the range I have discovered.